Hybrid grapevine rootstock

ABSTRACT

A new and distinct variety of grapevine rootstock is provided. It is characterized by its immunity to feeding by the nematode vector of grapevine fanleaf virus and to feeding by phylloxera. When grafted with scion cultivars, such as `Cabernet Sauvignon,` `Chenin blanc,` and `Carignane,` the variety may be planted in soil contaminated with viruliferous nematodes and/or phylloxera and will produce healthy fruit and excellent yields.

The present invention relates to a new and distinct rootstock variety ofgrapevine. More particularly the new variety, which has been named `VR039-16,` has been shown to effectively tolerate grapevine fanleaf virusand Xiphinema index, the nematode vector.

FIG. 1 shows a typical flower cluster form of the new variety.

FIG. 2 typifies the mature leaves of the new variety.

FIG. 3 shows the flowers of the new variety.

A serious problem which has faced the California grape industry for manyyears is the grapevine fanleaf virus -- Xiphinema index nematodecomplex. Soil fumigation treatments have had limited success incontrolling the vector spreading infectious degeneration. Frequentlysoil treatment has completely failed. When planted in soil infested withviruliferous X. index, Vitis vinifera grape cultivars become infectedwith the disease, and vines degenerate rapidly to a point where fruitset is reduced and crop production becomes twenty percent (20%) or lessthan that of normal healthy vines of the same cultivar.

When vinifera scions are grafted onto standard phylloxera resistantrootstocks that are in general use, such as `Harmony,` `Couderc 1613,``Rupestris St. George` (`du Lot`) and `Ganzin 1`, degeneration has notbeen prevented and oftentimes is exacerbated to a point where vines arevirtually cropless.

The grapevine of this invention was selected from a cross made in 1948between Vitis vinifera `Almeria` and V. rotundifolia male No. 2.Initially, the selection was tested for phylloxera resistance and thesuccess of those tests was reported in 1964. However, due to thedifficulty in propagating the selection, as compared with the standardphylloxera-resistant rootstocks, `VR 039-16` was not released. Interestin this vine was renewed when differential tolerance to infectiousdegeneration and X. index was observed. These observations led to theexperiments which have determined the immunity of `VR 039-16` to X.index feeding. Vines of `VR 039-16,` when grafted with scions ofsusceptible vinifera cultivars such as `Cabernet Sauvignon,` `Cheninblanc,` and `Carignane` and planted in infested soil have remaineddisease free and productive for at least seven (7) years. The tests wereaided by a new serological technique which permits rapid detection ofgrapevine fanleaf virus in grapevine tissues. The technique is known asenzyme-linked immunosorbent assay (ELISA). ELISA of tissues taken fromexperimental vines of `VR 039-16` at various stages of growth gave proofthat `VR 039-16` was virtually free of infectious degeneration.Throughout the extended test period crop yield and vine growth wereexcellent, and the clusters and berries obtained on `VR 039-16` stockdemonstrated complete freedom of virus infection. The scions on thestandard phylloxera-resistant rootstocks in the same tests as `VR039-16` displayed severe degeneration evidenced by low yields, smallerclusters and berries and reduced pruning weights.

`VR 039-16` was tested and has been found suitable for planting invineyards infected with viruliferous nematodes in the important winegrape areas of Napa and San Joaquin Counties in California. The varietyhas been asexually reproduced by cuttings and although difficult topropagate, propagation has been improved by the application of rootinghormones.

In addition to its immunity to nematode feeding `VR 039-16` is immune tophylloxera and resistant to most strains of root knot nematodes. It isdistinguished from its companion rootstock `VR 043-43` in that it isimmune to phylloxera, whereas, `VR 043-43` shows only tolerance. `VR039-16` differs from the standard phylloxera resistant rootstocks inthat it is somewhat more difficult to propagate and is immune to vectorfeeding. Also, `VR 039-16` is resistant to feeding by root knotnematodes, whereas `St. George` and `Ganzin 1` are not.

Definitive phenological and morphological characteristics of VR 039-16are as follows:

Flowers

Flowers staminate with sterile pollen and poorly developed anthers.Indistinct but well-formed stigma on most flowers. Flower cluster formsmall, 4-6 cm long. Stamens moderately reflexed with tendency towardsperfect flowering. Ovary small but well-formed. Sterile, with no fruitset.

Leaves

Leaves deeply three to five lobed. Both inferior and superior sinusesare open. Margin distinctly and uniformly dentate. Older leaves slightlytomentose with tufted hairs that tend to dehisce. Younger leaves withsoft long hairs on both upper and lower surface, more on upper surface.Mature leaves light to light yellow green. Vigorously growing shoot tipsalmost wooly white with tomentum.

Tendrils

Tendrils, long, slender and well-formed, often longer than leaf blades;these are bifid, with discontinuous arrangement of vinifera type.

Mature Wood

Mature wood tan in color, with persistent bark and prominent lenticels.Nodes with septum.

Time of bloom

Blooms late, 12 to 14 days later than Semillon, 10% bloom at Davis onMay 25, 1985.

We claim:
 1. The new and distinct variety of grapevine rootstock hereindescribed and illustrated and identified by the characteristicsenumerated above.